1. Field
This disclosure relates generally to split gate memories, and more specifically, to programming of split gate memories.
2. Related Art
Split gate memories are a type of non-volatile memory (NVM) that have, between the doped regions that are for use as sources and drains, a control gate and a select gate. The control gate is over the storage medium that may be a floating gate or a thin film storage layer of nanocrystals or nitride. The select gate is coupled to a word line and a bit line for selecting when the memory cell is to be read or programmed. A benefit of the split gate memory is low power programming and thus is better for low power applications. As is typical of NVM cells in general, endurance and data retention are important issues. Data retention, the time a cell will retain enough charge to be reliably read after programming, may be decisive in determining suitability for a particular use. For some automotive applications, data retention is exceptionally important. A cheaper solution may be of little consequence if the data retention requirement is not met. Use of nanocrystals helps because a weak spot that provides leakage may only affect a single nanocrystal while the others continue to hold charge and thus provide for the ability to be reliably read. No current leakage at all from a given nanocrystal, however, is difficult to achieve. Thus data retention of split gate memories still needs improvement in order to be usable in some applications.
Accordingly there is a need to provide for better data retention for split gate memories.